a well known shock isolating mount currently used in the automotive industry for securing and supporting the body or cab of a vehicle on its frame comprises two mating rings of elastically resilient material between which a body mounting part such as an ear protruding from the vehicle is engaged and clamped by a two-part spool that is seated on the vehicle frame and fixed to it by a threaded fastener. The spool parts have flanges which bear against the opposite sides of the mating rings and are threaded together so that by turning one spool part relative to the other the elastic rings and the body mounting part between them are clamped tightly between the flanges. One of the spool parts is a tubular spacer having an annular flange integral with a deep drawn tube that is internally left hand threaded. The other spool part is a thimble having an annular flange integral with a deep drawn tube that is externally left-hand threaded to fit inside and engage its thread with the screw thread of the tubular spacer. A torque nut is welded to the outer face of the thimble flange.
The mating elastic rings of the prior art are provided with an oblong projection and an oblong cavity so that they may be mated only when the projection and cavity are properly aligned.
This known shock mount is assembled by inserting the spacer tube through the center of one of the mating elastic rings, and through an opening in the body mounting part. The second mating elastic ring is then fitted over the end of the spacer tube. The end of the thimble tube is placed in the end of the spacer tube, and the thimble is turned to thread it into the spacer tube and clamp the elastic rings tightly together on the body mounting part. Then, the spool assembly and body part is seated in place on the vehicle frame, and the threaded fastener is passed up through an opening in the frame, through the tubes and the assembled spool parts, and is threaded into the nut welded onto the thimble until the entire assembly is fixed securely to the frame.
It has been found that several practical drawbacks impede effective fastening by the prior art assembly.
During production line assembly of the spool parts crossing and jamming of the left-hand thread can and sometimes does occur, preventing the assembly from clamping together properly. An additional drawback of the known assembly becomes apparent if cross-threading of the threaded fastener and the welded nut occurs, because torque applied to the fastener in an attempt to unscrew the threaded fastener can instead cause the left-hand threaded thimble to unscrew from the spacer, jamming the entire assembly so that the unit must be cut off. The jamming and cross-threading can slow or stop the production line, increasing manufacturing cost.
The problems associated with this known shock mount have been addressed in U.S. Pat. No. 4,720,075, issued Jan. 19, 1988, and in U.S. Pat. No. 4,783,039, issued Nov. 8, 1988, in both of which we are a co-inventor, and the disclosures of which are hereby incorporated by reference in their entirety.
These patents disclose a two-part telescoping spool including a spacer and a thimble. Two mating resilient rings are mounted on each of the spacer and thimble, and the support part of a vehicle frame is disposed between these rings. An elongate fastening device engages the thimble and allows the simultaneous securing of a body mounting part and clamping of the support part. The thimble and the spacer have mutually engaging means for limiting rotation of either of them relative to the other. Preferably, the spacer tube is formed at its axial end opposite the spacer flange into a polygon, as viewed in cross-section. The thimble tube is formed at the tube shoulder adjacent the thimble flange into a complementary polygonal shape, so that the thimble polygon formation can be received in the spacer polygon formation, preventing rotation of the two members relative to each other. The two-part spool further includes means on the inside of the spacer member for engaging an end portion of the thimble member for resisting separation of the spacer and thimble members when the thimble tube is received in the spacer tube. The engaging means comprises a plurality of inward protrusions, which is disclosed as a six tooth washer, located inside the spacer tube so that the teeth engage an enlarged end of the thimble tube.
The present invention improves upon the six tooth washer disclosed in our prior applications, and provides a retaining spring element adapted for repeated coupling and uncoupling of the parts of the shock mount.